Tech Search

Say you feel sick, but before you see a doctor you search the Web for information, or blog or Twitter about the flu. Your worries will be detected by companies prowling the Internet for disease trends.

If you actually come down with the flu, and the doctors want to know who you've been in physical contact with, your trusty cellphone could soon tell them.

And someday, scientists hope, this "infodemiology" might help forecast and track a flu epidemic the way experts monitor the weather.

As health officials gear up for the flu season amid the global H1N1 pandemic, technology and new forms of Internet social interaction are transforming how such outbreaks are monitored.

"All these things really change the way that we can manage diseases," said Alessandro Vespignani, professor of informatics at Indiana University. "It's not just . . . a passive approach, where we just wait for the disease and then try to do something."

Currently, most disease tracking is done through doctors reporting cases of illness they have seen. It's a reliable system but often involves a lag time of a week or more in reporting and does not account for people who don't go to the doctor.

Internet surveillance raises questions about privacy and confidentiality. But experts say it has the advantage of speed and can augment the current system by detecting sick people who might not see a doctor.

Google's public Flu Trends system, for example, is designed to pick up early clues by tracking and analyzing Internet searches for flu information. "We keep track of what queries have been asked, and how often," said Roni Zeiger, the Flu Trends product manager. Because people often search for information on the Web before going to a doctor, the system can provide an early warning of trouble, he said.

During the 2007-08 flu season Google used an early version of the system that consistently detected flu rates one to two weeks ahead of official reports, the company said in a paper published in February.

Other companies and programs scan live Web chatter for mentions of, or reports about, the flu.

Boston-based HealthMap's automated system sends out an hourly Web "crawler" that hunts for flu information in seven languages.